<PAGE>

                                                                    EXHIBIT 4.33


                            SHARE PURCHASE AGREEMENT
                                (TO BE NOTARIZED)


                                     between


                               DR. BERND PITSCHAK
                       Vormholzer Ring 69c, 58456 Witten,

                                                              - the "SELLER 1" -

                             PROF. DR. KARL H. KLUG
                        Bauordenweg 7, 45481 Mulheim/Ruhr

                                                              - the "SELLER 2" -

             CREAVIS GESELLSCHAFT FUR TECHNOLOGIE UND INNOVATION MBH
                Paul-Baumann-StraBe 1, Building 141/15, 45764 Marl

                                                              - the "SELLER 3" -
on the one hand
                                       and


                              HYDROGENICS GMBH I.G.
                       Luggendelle 19, 45894 Gelsenkirchen
                                                             - the "PURCHASER" -

                             HYDROGENICS CORPORATION
             5984 McLaughlin Road, Mississauga, ON, L5R 1B8, Canada,

                                                               - "HYDROGENICS" -
on the other hand.

Seller 1, Seller 2 and Seller 3 together are referred to as "SELLERS". Each of
the Sellers and the Purchaser are also referred to as a "PARTY"; Sellers and
Purchaser together are also referred to as "PARTIES".


<PAGE>


TABLE OF CONTENTS

<TABLE>
<S>                                                                                                       <C>
PREAMBLE...................................................................................................3

Article 1 Sale and Transfer of the ENKAT-Shares............................................................4
Article 2 Purchase Price for the ENKAT-Shares..............................................................4
Article 3 Sale and Assignment of Payment Claims of Seller 3 under Shareholder Loans........................5
Article 4 Sale and Assignment of Outstanding Compensation of Seller 2......................................5
Article 5 Further Agreements with Seller 1 and Seller 2....................................................5
Article 6 Guarantees of Sellers 1 and 2....................................................................7
Article 7 Breach of Guarantees of Sellers 1 and 2.........................................................13
Article 8 Guarantees of Seller 3; Breach of Guarantees....................................................14
Article 9 Competition Restraint...........................................................................16
Article 10 Miscellaneous..................................................................................16

LIST OF EXHIBITS..........................................................................................18

Exhibit 5.1...............................................................................................19
Exhibit 5.2...............................................................................................20
Exhibit 5.3(b)............................................................................................21
Exhibit 6.5(h)............................................................................................23
Exhibit 6.3(c)............................................................................................24
Exhibit 6.7(a)............................................................................................25
Exhibit 6.9(b)............................................................................................26
</TABLE>




<PAGE>


                                    PREAMBLE

1.       ENKAT GmbH - Gesellschaft fur Energiemanagement und Katalyse is a
         limited liability company under German law (Gesellschaft mit
         beschrankter Haftung), registered in the commercial register maintained
         at the lower court of Gelsenkirchen-Buer under registration no. HR B
         1849 and having its domicile in Gelsenkirchen, Germany ("ENKAT"). ENKAT
         has a registered capital of DM 100,000.00 which is divided into five
         (5) shares with a nominal value of DM 100.00, DM 37,000.00, DM
         12,900.00, DM 25,100.00 and DM 24,900.00 each (hereinafter each an
         "ENKAT-SHARE" and together the "ENKAT-SHARES"). ENKAT is active in the
         field of planning and marketing of services in the area of energy
         management and catalyzation (Katalyse).

         Sellers have submitted to Purchaser a certified copy of an excerpt from
         the commercial register which reflects the current register entries of
         facts and of all circumstances in need of registration for ENKAT.

2.       Seller 1 is a shareholder of ENKAT, holding two (2) shares with a
         nominal value of DM 100.00 and DM 37,000.00; Seller 1 also is the
         current sole managing director (Geschaftsfuhrer) of ENKAT.

3.       Seller 2 holds two (2) shares in ENKAT with a nominal value of DM
         12,900.00 and DM 25,100.00 and works for ENKAT on the basis of a
         consultancy agreement.

4.       Seller 3 is a limited liability company under German law (Gesellschaft
         mit beschrankter Haftung), registered in the commercial register
         maintained at the lower court of Marl under registration no. HR B 3390
         and having its domicile in Marl, Germany. Seller 3 holds one (1) share
         in ENKAT with a nominal value of DM 24,900.00.

5.       Purchaser is a limited liability company under German law (Gesellschaft
         mit beschrankter Haftung) in foundation, to be registered in the
         commercial register maintained at the lower court of Gelsenkirchen,
         Germany, and having its domicile in Gelsenkirchen, Germany. Purchaser
         is a wholly owned subsidiary of Hydrogenics.

6.       Sellers intend to sell to Purchaser, and Purchaser intends to purchase
         from Sellers, the ENKAT-Shares.

Now, therefore, the Parties agree as follows (hereinafter the "AGREEMENT"):


<PAGE>


                                    ARTICLE 1
                      SALE AND TRANSFER OF THE ENKAT-SHARES

(1)      With effect as of May 1, 2002 (the "EFFECTIVE DATE"), Sellers hereby
         sell and, subject to the receipt of the Purchase Price (as defined in
         Article 2 below), transfer to Purchaser the ENKAT-Shares with all
         rights and obligations pertaining thereto. Purchaser hereby accepts
         this sale and transfer. In any event Sellers hereby sell and, subject
         to the receipt of the Purchase Price (as defined in Article 2 below),
         transfer to Purchaser all existing shares in ENKAT regardless of the
         nominal amount; Purchaser hereby accepts such sale and transfers.

(2)      As among the Parties, the ENKAT-Shares shall be deemed transferred to
         Purchaser with economic effect as of January 1, 2002.

(3)      Sellers hereby consent to the transfer of the ENKAT-Shares in their
         capacity as shareholders in accordance with ss. 8 of the articles of
         association of ENKAT. As a precautionary measure, each Seller hereby
         waives any and all rights to sell the ENKAT-Shares, any pre-emptive
         rights or rights of first refusal to which he/it is entitled with
         regard to the ENKAT-Shares, irrespective on what legal grounds.


                                    ARTICLE 2
                       PURCHASE PRICE FOR THE ENKAT-SHARES

(1)      The purchase price for the ENKAT-Shares amounts to EUR 300,000.00 (in
         words: Euro three hundred thousand) (hereinafter referred to as the
         "PURCHASE PRICE").

(2)      The Purchase Price becomes payable on the Effective Date. It is payable
         to Sellers by delivery to each Seller of a certified check or a bank
         draft in the amounts indicated below:

         o        to Seller 1, an amount of EUR 111,300.00 (in words: Euro one
                  hundred eleven thousand three hundred);

         o        to Seller 2, an amount of EUR 114,000.00 (in words: Euro one
                  hundred fourteen thousand); and

         o        to Seller 3, an amount of EUR 74,700.00 (in words: Euro
                  seventy-four thousand seven hundred).



<PAGE>

                                    ARTICLE 3
                SALE AND ASSIGNMENT OF PAYMENT CLAIMS OF SELLER 3
                             UNDER SHAREHOLDER LOANS

(1)      With effect as of the Effective Date, Seller 3 hereby sells and assigns
         to Purchaser its claims on repayment of the outstanding balance
         (including accrued interest) under the two shareholder loans given by
         Seller 3 to ENKAT under the loan agreements dated January 20, 1998 and
         October 28/29, 1998 respectively. Purchaser hereby accepts this sale
         and the assignments.

(2)      The purchase price for the claims under para. (1) above amounts to EUR
         208,282.55 (equals DM 407,365.26). The purchase price is payable on the
         Effective Date by delivery of a certified check or a bank draft to
         Seller 3.


                                    ARTICLE 4
           SALE AND ASSIGNMENT OF OUTSTANDING COMPENSATION OF SELLER 2

(1)      With effect as of the Effective Date, Seller 2 hereby sells and assigns
         to Purchaser all his claims on payment of the accrued outstanding
         compensation of Seller 2 under his consultancy agreement with ENKAT
         dated October 23, 1998 (with amendments of June 26, 2000 and January
         15, 2001) until the Effective Date. Purchaser hereby accepts this sale
         and assignment.

(2)      The purchase price for the claims under para. (1) above amounts to EUR
         81,807.96. The purchase price is payable on the Effective Date by
         delivery of a certified check or a bank draft to Seller 2.


                                    ARTICLE 5
                  FURTHER AGREEMENTS WITH SELLER 1 AND SELLER 2

(1)      On the Effective Date Purchaser will and is obliged to use its
         influence as new sole shareholder of ENKAT that ENKAT enters into a
         service agreement with Seller 1 in accordance with the terms and
         conditions as set forth in the draft service agreement attached as
         Exhibit 5.1; Seller 1 agrees to enter into such agreement with ENKAT.


<PAGE>

(2)      On the Effective Date Seller 2 agrees to enter into an exclusive,
         irrevocable, world-wide, license agreement with Hydrogenics concerning
         his pending German patent application DE 101 09 983 A1, filed with the
         German Patent Office, Munich (Deutsches Patentamt), on March 1, 2001,
         with respect to the invention "Electro-catalytic Reformer for the
         Synthesis Gas Production (Elektrokatalytischer Reformer fur die
         Synthesegaserzeugung)" in accordance with the terms and conditions as
         set forth in the draft license agreement attached as Exhibit 5.2.

(3)      Seller 2 currently is employed as holder of a chair for Thermodynamics
         (Warmelehre) at the University of Applied Sciences of Gelsenkirchen
         (Fachhochschule Gelsenkirchen). Seller 2 agrees, to the extent legally
         permissible, to devote his entire working capacity and all of his
         professional knowledge and expertise to ENKAT and, in the light
         thereof, coordinate his activities in connection with his employment at
         the University of Applied Sciences (Fachhochschule Gelsenkirchen) in
         the future. Should it be admissible for Seller 2 to be appointed
         managing director of ENKAT, or should he have given up his
         aforementioned activity at the University of Applied Sciences
         (Fachhochschule Gelsenkirchen) he shall have the right to become
         managing director of ENKAT upon the same terms and conditions as Seller
         1.

         Seller 2 and Purchaser agree that the consultancy agreement between
         Seller 2 and ENKAT dated October 23, 1998 (with amendments of June 26,
         2000 and January 15, 2001) (the "CONSULTANCY AGREEMENT") shall be
         amended as follows:

         (a)      In ss. 2 (Term of the Agreement - Dauer des Vertrages) of the
                  Consultancy Agreement, the base term of five (5) years
                  (Grundvertragsdauer) of the agreement as defined in sentence 1
                  shall start anew on the Effective Date. Sentence 2 shall be
                  deleted; instead a new sentence shall be inserted under which
                  the subsequent periods of automatic prolongation after expiry
                  of the initial term, unless the Consultancy Agreement is
                  terminated by either Party on five (5) months' prior written
                  notice to the end of each term, shall be each time one (1)
                  year.

         (b)      ss. 3 (Compensation - Vergutung) of the Consultancy Agreement
                  shall be deleted; instead the following clause shall be
                  inserted:

                           "Prof. Klug shall receive compensation in the gross
                           amount of EUR 112,600.00 (in words: Euro one hundred
                           and twelve thousand six hundred), payable in twelve
                           (12) equal instalments at the end of each calendar
                           month. In addition, he shall be entitled to payments
                           of


<PAGE>

                           a performance bonus in accordance with the attached
                           bonus scheme."

                  The aforementioned bonus scheme for the years 2002 - 2006 is
                  attached hereto as Exhibit 5(3)(b).

         (c)      ss. 8 (3) of the Consultancy Agreement, containing an
                  obligation of ENKAT and Seller 2 to regularly review the
                  agreement and re-draft it annually, shall be deleted.

         On the Effective Date Purchaser will and is obliged to use its
         influence as new sole shareholder of ENKAT that ENKAT enters into an
         amendment of the Consultancy Agreement in accordance with the terms and
         conditions as set forth above under lit. (a) to (c); Seller 2 agrees to
         enter into such an amendment of the Consultancy Agreement.

(4)      In addition, Hydrogenics will grant to Seller 2 25,000 stock options
         pursuant to its actual stock option plan. These stock options shall
         exclusively be governed by the stock option agreement between Seller 2
         and Hydrogenics and not be part of this Agreement. Further, Hydrogenics
         will take out life insurances for Sellers 1 and 2 for a period of five
         (5) years on a declining scale to cover the entitlements under the
         service agreement with Seller 1 referred to in Article 5(1) and the
         amended Consultancy Agreement of Seller 2.

(5)      Hydrogenics hereby warrants by way of an independent guarantee
         (selbstandiges Garantieversprechen) pursuant to Section 311 (1) German
         Civil Code (BGB) the fulfillment of all obligations of Purchaser under
         this Agreement towards Sellers 1 and 2.


                                    ARTICLE 6
                          GUARANTEES OF SELLERS 1 AND 2

Sellers 1 and 2 hereby warrant by way of an independent guarantee (selbstandiges
Garantieversprechen) pursuant to Section 311 (1) German Civil Code (BGB) the
following, and this in relation to the time of signing of this Agreement and as
per the Effective Date (if no other point in time or time period is referred to
in the following):

(1)      Legal Situation


<PAGE>

         (a)      ENKAT is a limited liability company, duly established and
                  validly existing under German law. ENKAT does not hold any
                  direct or indirect participations in other companies. The
                  statements contained in number 1. of the Preamble of this
                  Agreement are accurate in every respect. ENKAT does not hold
                  any direct or indirect participations in other companies. The
                  ENKAT-Shares of Sellers 1 and 2 exist in the amounts set out
                  in numbers 2. and 3. of the Preamble of this Agreement and are
                  fully paid-up. The share capital has not been reduced by
                  repayments or any comparable processes.

         (b)      Each of the Sellers 1 and 2 is the sole and unrestricted owner
                  of those ENKAT-Shares sold by him as described in numbers 2.
                  and 3. of the Preamble of this Agreement. The ENKAT-Shares of
                  Seller 1 and 2 are duly authorized and validly issued. There
                  are no restrictions to sell and transfer the ENKAT-Shares to
                  Purchaser in accordance with this Agreement. No third parties
                  are entitled to exercise pre-emptive or similar rights in case
                  of a sale and transfer of the ENKAT-Shares of Seller 1 and 2.
                  The ENKAT-Shares of Seller 1 and 2 are not pledged or
                  otherwise encumbered with rights of third parties (within the
                  meaning of ss.ss. 433 (1) 2, 435 of the German Civil Code
                  (BGB).

         (c)      This Agreement and its implementation does not constitute a
                  breach of any agreement by which Sellers 1 and 2 are bound.

(2)      Financial Situation

         (a)      The following annual accounts of ENKAT have been prepared in
                  accordance with generally accepted accounting principles in
                  Germany (Grundsatze ordnungsgema(beta)er Buchfuhrung und
                  Bilanzierung), and having regard to the principle of
                  continuity of accounting and valuation (taking due account of
                  the accounting principles applied in previous years):

                  -        Audited annual accounts of ENKAT as per December 31,
                           2000;

                  -        Audited annual accounts of ENKAT as per December 31,
                           2001 (the "2001 ACCOUNTS").

         (b)      As per December 31, 2001, ENKAT had no liabilities other than
                  those shown in the 2001 Accounts; since then, ENKAT has not
                  incurred any liabilities or obligations (whether accrued or
                  absolute, contingent or otherwise), which continue to be
                  outstanding, except for those liabilities



<PAGE>

                  and obligations listed in Exhibit 6.2(b) or which were
                  incurred in the ordinary course of business. It is understood
                  that Sellers 1 and 2 give no warranty on future revenues or
                  profits.

(3)      Assets

         (a)      ENKAT is the owner of all assets shown in the 2001 Accounts,
                  free from third party claims (excepting customary retention of
                  title), except as for assets disposed of in the ordinary
                  course of business since January 1, 2002.

         (b)      All assets used by ENKAT as well as the operation, storage and
                  handling thereof are effected in accordance with applicable
                  laws and legal provisions, and this in particular also with
                  regard to environmental and other public law provisions,
                  regulations and permits.

         (c)      As of the date of this Agreement, ENKAT has no accounts
                  receivables which are 90 days or more past due, except for
                  those listed in Exhibit 6.3(c).

(4)      Litigation/Compliance with Applicable Law

         (a)      ENKAT is - as of the signing of this Agreement - not a party
                  to any legal action, whether as plaintiff or defendant
                  (including any arbitration proceedings), nor are there any
                  other legal, arbitration or other proceedings in which it is
                  involved. As of the date of signing of this Agreement, Sellers
                  1 and 2 have no knowledge of any administrative proceedings or
                  investigations imminent or pending against ENKAT, including
                  any such proceedings under competition law. As of the signing
                  of this Agreement no claims have been asserted or threatened
                  against ENKAT, which would involve a one-off or annual burden
                  of more than EUR 25,000.00 on ENKAT. As of the date of signing
                  of this Agreement, Sellers 1 and 2 are not aware of any
                  factual circumstances on which such claims could be based
                  except for possible litigation arising from the former
                  business relationship of ENKAT with ATT.

         (b)      ENKAT is authorized without restrictions and has been granted
                  all permits which are necessary to continue its present
                  business operations. There are no public law authorizations
                  which, due to the sale envisaged with this Agreement, could be
                  modified, withdrawn or revoked. In all material aspects, the
                  operations of ENKAT have been, and are now being, conducted in
                  compliance with the laws of each jurisdiction in which



<PAGE>

                  ENKAT carries on business. Sellers 1 and 2 have no knowledge
                  of ENKAT being in breach of any provisions under public law,
                  competition law or laws for the protection of intellectual
                  property rights.

(5)      Contracts

         ENKAT is not a party to any written or oral agreement or contract of
         the following kind:

         (a)      except for the lease agreement with Erwin Kahrmann concerning
                  the building in Gelsenkirchen-Buer dated October 17, 2000, the
                  Consultancy Agreement between ENKAT and Seller 2 dated October
                  23, 1998 and except for employment contracts, any rental or
                  lease agreements or other agreements the contract or
                  obligation value whereof exceeds in each instance EUR
                  25,000.00 p.a.;

         (b)      agreements with sales representatives, commission merchants,
                  contract dealers or other distributors;

         (c)      any contracts or other obligations limiting or excluding the
                  right of ENKAT to compete;

         (d)      loan agreements, except for the shareholder loans given by
                  Seller 3 to ENKAT under the loan agreements dated January 20,
                  1998 and October 28/29, 1998;

         (e)      any agreement granting the respective counterparty a right to
                  terminate or change the agreement in case shares of ENKAT are
                  to be sold;

         (f)      any guarantee, warranty or other agreements or unilateral
                  transactions whereby collateral is granted for or the
                  assumption of third party liabilities, any futures contracts,
                  currency transactions or swap agreements;

         (g)      any agreements or contracts which grant to third parties any
                  rebates, discounts or any other deductions than those
                  previously granted in the ordinary course of business;

         (h)      except for the employment agreement between ENKAT and Peter
                  Pabst dated January 29, 2001, any contracts with employees
                  with an annual salary exceeding EUR 25,000.00 (including any
                  percentage of profits or a bonus paid);


<PAGE>

         (i)      any agreement or obligation outside the scope of the ordinary
                  business.

(6)      Employees

         (a)      ENKAT has not more than those employees listed in Exhibit
                  6.6(a); for every employee Exhibit 6.6(a) furthermore lists
                  the titles, service record and material terms of employment,
                  including current wages, salaries or hourly rate of pay and
                  bonus (whether monetary or otherwise) paid since December 31,
                  2001, the date upon which such wage, salary, rate or bonus
                  became effective and the date upon which each such employee
                  was first hired by ENKAT.

         (b)      Except as shown in Exhibit 6.6(b), ENKAT is not a party to any
                  voluntary pension promises or direct insurances, agreements on
                  commissions or bonuses, employment agreements with extended
                  termination periods compared with bargaining agreements,
                  agreements with unions, shop agreements or agreements with
                  professional associations (e.g. employers' associations).

         (c)      ENKAT has been and is being operated in full compliance with
                  all laws relating to employees. There have been no claims, nor
                  are there, to the knowledge of Sellers 1 and 2, any threatened
                  complaints under such laws against ENKAT, except for possible
                  non-compliance issues relating to the status of Mr. Reichardt
                  as a free lance employee.

(7)      Intellectual Property Rights /Registrations

         Except as shown in Exhibit 6.7(a), the business operations of ENKAT do
         not involve the use of intellectual property rights. The list in
         Exhibit 6.7(a) is exhaustive and all such intellectual property rights
         have been registered for ENKAT. ENKAT is the sole legitimate owner of
         the respective intellectual property rights. To the best of the
         knowledge of Sellers 1 and 2 the intellectual property rights listed in
         Exhibit 6.7(a) are - in their geographical respective area of validity
         - not subject to third party objections. There are no respective legal
         actions pending or imminent nor to be expected based on other
         circumstances.

(8)      Agreements between Sellers 1 and 2 and ENKAT and among Sellers 1 and 2

         (a)      There are no contracts existing between one or several of
                  Sellers 1 and 2 on the one hand, and ENKAT on the other hand,
                  except for the service



<PAGE>

                  agreement between ENKAT and Seller 1 dated October 7, 1997 and
                  the Consultancy Agreement between ENKAT and Seller 2 dated
                  October 23, 1998.

         (b)      Except for the articles of association of ENKAT dated October
                  29, 1998, there are no contracts among Sellers 1 and 2 which
                  relate to ENKAT.

(9)      Existing Contracts; Insurance

         (a)      The contracts and agreements to which ENKAT is a party and
                  which are material for its business operation, are in full
                  force and effect, unamended, and no material default exists
                  under such contracts and agreements on the part of ENKAT, or,
                  to the knowledge of Sellers 1 and 2, on the part of any other
                  party to such contracts and agreements.

         (b)      ENKAT maintains the policies of insurance which are listed in
                  Exhibit 6.9(b). ENKAT is not in default, as to the payment of
                  premiums, under the terms of such policies. There exist no
                  open insurance claims other than those claims listed in
                  Exhibit 6.9(b).

(10)     Tax

         (a)      All tax declarations or tax applications which were to be
                  filed by ENKAT until the Effective Date, have been filed and
                  all statements made therein are correct and complete.

         (b)      All amounts which, pursuant to these tax declarations or
                  filings, are to be paid by ENKAT (including interest and other
                  ancillary duties) and which relate to the time period before
                  the Effective Date, have been paid in full and in time. For
                  unpaid taxes which relate to the period until December 31,
                  2001, sufficient liabilities or accruals are shown in the 2001
                  Accounts. ENKAT has, in accordance with statutory provisions,
                  in full and in time, withheld and paid to the tax authorities,
                  social security institutions or health insurance institutions,
                  all wage taxes as well as employees' shares for social
                  security and other social benefits (hereinafter collectively
                  referred to as the "EMPLOYMENT CHARGES") for all time periods
                  until the Effective Date. For Employment Charges relating to
                  the period until December 31, 2001 and which are not paid,
                  appropriate obligations or provisions have been stated in the
                  2001 Accounts therefore.

(11)     Transactions since January 1, 2002 until the Effective Date


<PAGE>

         Within the period between January 1, 2002 and the Effective Date the
         following will have been complied with:

         (a)      the business of ENKAT shall be conducted in the ordinary and
                  normal course, consistent with past practice and in accordance
                  with proper business principles, and no extraordinary
                  transactions shall be effected;

         (b)      ENKAT shall not dispose of any assets;

         (c)      the scope and contents of the business activities shall not be
                  changed substantially;

         (d)      no profit distributions shall be declared or made (including
                  hidden profit distributions);

         (e)      no increase in the remuneration, no change of other employment
                  conditions and no pension commitments or changes thereof for
                  any of the employees (including managing directors) shall be
                  effected or promised;

         (f)      ENKAT shall not (i) conclude or use loans or (ii) enter into
                  contracts which have a total value of more than EUR 25,000.00
                  p.a. each;

         (g)      the purchasing and payment practice shall not be changed;

         (h)      no special discounts shall be granted to customers.


                                    ARTICLE 7
                     BREACH OF GUARANTEES OF SELLERS 1 AND 2

(1)      If any of the guarantees given by the Sellers 1 and 2 under Article 6
         is incorrect, the following shall apply:

         Sellers 1 and 2 shall place Purchaser or (at Purchaser's choice), if
         ENKAT has incurred the damage, ENKAT, in that position as if the
         guarantees had been correct. If and to the extent that Sellers 1 and 2
         within one (1) month fail to put the respective party in the position
         as set forth in the Agreement, or if it is impossible to put that party
         in that position, Purchaser shall be entitled to claim monetary damages
         up to an aggregate amount of EUR 214,000.00. This limitation shall not
         apply, however, to the guarantees given under Article 6(1).


<PAGE>

(2)      To the extent that Sellers 1 and 2 have represented in this Agreement
         that ENKAT is free of liabilities, Sellers 1 and 2 shall indemnify and
         hold harmless ENKAT from any liabilities (including the cost for legal
         advisers), which exist or are asserted contrary to this representation.

(3)      Claims under this Article 7 shall be time-barred

         (a)      in respect of incorrectness of any of the guarantees detailed
                  in Article 6(1) after ten (10) years from the Effective Date;

         (b)      in respect of incorrectness of the guarantees detailed in
                  Article 6(10) six (6) months after tax assessments have become
                  final or, if no final payment order is made, six (6) months
                  after the respective tax liability is barred by statute of
                  limitation in accordance with the law;

         (c)      in respect of any other claims under this Article 7 after two
                  (2) years from the Effective Date.

         The limitation period shall be suspended by raising a claim in writing
         vis-a-vis Sellers 1 and 2. Should there be a written notice of a claim
         before the end of the limitation period, the limitation period for the
         respective claim shall be extended by another three (3) months. After
         such additional three (3) months, the claim will be time-barred unless
         the limitation period is interrupted in accordance with the law.


                                    ARTICLE 8
                  GUARANTEES OF SELLER 3; BREACH OF GUARANTEES

(1)      Seller 3 warrants by way of an independent guarantee (selbstandiges
         Garantieversprechen) pursuant to Section 311 (1) German Civil Code
         (BGB), and this in relation to the time of signing of this Agreement
         and as per the Effective Date, that:

         (a)      The ENKAT-Share held by Seller 3 exists in the amount set out
                  in number 4. of the Preamble of this Agreement and is fully
                  paid-up. The share capital has not been reduced by repayments
                  or any comparable processes.

         (b)      Seller 3 is the sole and unrestricted owner of the ENKAT-Share
                  sold by it as described in number 4. of the Preamble of this
                  Agreement. This ENKAT-Share is duly authorized and validly
                  issued. There are no restrictions to sell and transfer this
                  ENKAT-Share to Purchaser in accordance with this



<PAGE>

                  Agreement. No third parties are entitled to exercise
                  pre-emptive or similar rights in case of a sale and transfer
                  of this ENKAT-Share. This ENKAT-Share is not pledged or
                  otherwise encumbered with rights of third parties (within the
                  meaning of ss.ss. 433 (1)2, 435 of the German Civil Code
                  (BGB).

         (c)      This Agreement and its implementation does not constitute a
                  breach of any agreement by which Seller 3 is bound.

         (d)      Seller 3 has the corporate power and authority to sell its
                  ENKAT-Share under this Agreement and to enter into this
                  Agreement. All corporate actions which are necessary for the
                  sale and transfer of its ENKAT-Share have been, or prior to
                  the Effective Date will be, taken.

(2)      If any of the guarantees given by Seller 3 under Article 8(1) is
         incorrect, the following shall apply:

         Seller 3 shall place Purchaser or (at Purchaser's choice), if ENKAT has
         incurred the damage, ENKAT, in that position as if the guarantees had
         been correct. If and to the extent that Seller 3 within one (1) month
         fails to put the respective party in the position as set forth in the
         Agreement, or if it is impossible to put that party in that position,
         Purchaser shall be entitled to claim monetary damages. Seller 3 shall
         in no event be liable for any consequential damages (Folgeschaden),
         lost profits (entgangener Gewinn), damages incidental to any breach or
         non-fulfillment of the independent guarantees or any internal costs and
         expenses incurred by the Purchaser.

(3)      Purchaser and Seller 3 are in agreement that the remedies that
         Purchaser or ENKAT may have against Seller 3 for breach of its
         obligations set forth in this Agreement are solely governed by this
         Agreement, and the remedies provided for by this Agreement shall be the
         exclusive remedies available to Purchaser or ENKAT. Any right of
         Purchaser to withdraw (zurucktreten) this Agreement or to require the
         winding up of the transaction contemplated hereunder (e.g. by way of
         gro(beta)er Schadenersatz or Schadenersatz statt der Leistung), any
         claims for breach of pre-contractual obligations (culpa in contrahendo,
         including but not limited to, claims arising under Sections 241 (2),
         311 (2) (3) German Civil Code) or ancillary obligations (positive
         Forderungsverletzung, including but not limited to, claims arising
         under Sections 280, 282 German Civil Code), frustration of contract
         pursuant to Section 313 German Civil Code (Storung der
         Geschaftsgrundlage), all remedies of Purchaser for defects of the
         Object of Sale under Sections 437 through 441 German Civil Code and any
         and all other statutory rights and remedies, if any, are hereby
         expressly excluded and waived by Purchaser, except



<PAGE>

         claims for willful deceit (arglistige Tauschung) and other intentional
         breaches of contract (vorsatzliche Vertragsverletzungen). Purchaser and
         Seller 3 are in agreement that Seller 3's guarantees are only designed
         for the specific remedies of Purchaser set forth in this Article 8
         above and the restrictions contained in this Article 8 and that Seller
         3's guarantees shall not serve to provide Purchaser with any other
         claims than those set forth in this Agreement.

(4)      Claims under this Article 8 shall be time-barred in respect of
         incorrectness of any of the guarantees detailed in this Article 8(1)
         after ten (10) years from the Effective Date.


                                    ARTICLE 9
                              COMPETITION RESTRAINT

(1)      For a period of three (3) years after the Effective Date, Sellers 1 and
         2 shall not, directly or indirectly, establish a business which
         directly competes with the business conducted by ENKAT on the date
         hereof, or acquire a majority interest (in equity or votes) in an
         enterprise which is engaged in a business which directly competes with
         the business presently conducted by ENKAT.

(2)      This competition restraint does not apply to Seller 3.


                                   ARTICLE 10
                                  MISCELLANEOUS

(1)      All transfer taxes, fees, notarial fees and charges payable in
         connection with the execution and implementation of this Agreement
         shall be borne by Purchaser. Each Party shall pay its own expenses,
         including the fees of its advisors, incurred in connection with this
         Agreement.

(2)      This Agreement (including all Exhibits attached hereto, which shall
         form an integral part of this Agreement) contains the entire agreement
         between the Parties with respect to the subject matter hereof and
         supersedes all prior agreements and understandings with respect
         thereto.

(3)      Any provision of this Agreement may be amended or waived if, and only
         if, such amendment or waiver is in writing and signed, or any other
         stricter form which is required by law in the case of an amendment, by
         each of the Parties hereto, or in the



<PAGE>

         case of a waiver, by the Party against whom the waiver is to be
         effective. This also applies to any amendments to this Article 10(4).

(4)      Should any provision of this Agreement, or any provision to be
         incorporated in the future, be or become invalid or unenforceable, the
         validity of the balance of this agreement shall not be effected
         thereby. The same applies if this Agreement contains any omissions. In
         lieu of the invalid or unenforceable provision or in order to complete
         any omission, a fair provision shall apply which, to the extent legally
         permissible, comes as close as possible to what the Parties had
         intended or would have intended, according to the spirit and purpose of
         this Agreement, if they had considered the matter at the time this
         Agreement was executed. The same applies if the provision is invalid
         because of the stipulated scope or time period.

(5)      This Agreement shall be governed by, and construed in accordance with,
         the laws of the Federal Republic of Germany. The courts of Frankfurt am
         Main, Germany, shall have exclusive jurisdiction.


Sellers declared: ENKAT does not own real estate.


The notary shall notify ENKAT of the transfer of the shares according to Article
1(4) of this Agreement, in accordance with Section 16 (1) German Act on Limited
Liability Companies (GmbHG).

The above protocol and the Exhibits were read to the persons appearing by the
acting notary and approved by the persons appearing and signed by the persons
appearing and the notary as follows:

/s/ DR. MICHAEL TIGGES, acting in the name and on behalf of Dr. Bernd Pitschak
    and Dr. Karl Klug

/s/ DR. JORG STREITFERDT, acting in the name and on behalf of Creavis GmbH

/s/ DR. ROLAND MASSE, acting in the name and on behalf of Hydrogenics

/s/ DR. KARSTEN MULLER -- EISING, notary