<PAGE>

                                                                     EXHIBIT 4.1

Number                  Catalytica Energy Systems, Inc.               Shares

COMMON STOCK                                                        COMMON STOCK



             INCORPORATED UNDER THE LAWS OF THE STATE OF DELAWARE

                                            SEE REVERSE FOR CERTAIN RESTRICTIONS

                                            CUSIP 148884 10 9
This certifies that         is the owner of

  fully paid and non-assessable shares of common stock, $.001 PAR VALUE, of

                        Catalytica Energy Systems, Inc.

transferable only on the books of the Corporation by the holder hereof, in
person or by duly authorized attorney, upon surrender of this certificate
properly endorsed. This certificate is not valid unless countersigned and
registered by the Transfer Agent and Registrar.

   In Witness Whereof, the Corporation has caused this certificate to be signed
with the facsimile signatures of its duly authorized officers and to be sealed
with the facsimile seal of the Corporation.

   Dated:

                                    [SEAL]


                Secretary                       Chief Executive Officer


COUNTERSIGNED AND REGISTERED:
                   CHASEMELLON SHAREHOLDER SERVICES, L.L.C.
                                                    TRANSFER AGENT AND REGISTRAR



                                         BY:

                                             AUTHORIZED SIGNATURE

<PAGE>

                        CATALYTICA ENERGY SYSTEMS, INC.

     THE CORPORATION IS AUTHORIZED TO ISSUE TWO CLASS OF STOCK, COMMON STOCK AND
PREFERRED STOCK. THE BOARD OF DIRECTORS OF THE CORPORATION IS AUTHORIZED TO
DETERMINE OR ALTER THE POWERS, PREFERENCES AND RIGHTS AND THE QUALIFICATIONS,
LIMITATIONS OR RESTRICTIONS GRANTED TO OR IMPOSED UPON ANY WHOLLY UNISSUED
SERIES OF PREFERRED STOCK, AND WITHIN THE LIMITATIONS OR RESTRICTIONS STATED IN
ANY RESOLUTION OR RESOLUTIONS OF THE BOARD OF DIRECTORS ORIGINALLY FIXING THE
NUMBER OF SHARES CONSTITUTING ANY SERIES, TO INCREASE OR DECREASE (BUT NOT BELOW
THE NUMBER OF SHARES OF ANY SUCH SERIES THEN OUTSTANDING) THE NUMBER OF SHARES
OF ANY SUCH SERIES SUBSEQUENT TO THE ISSUE OF SHARES OF THAT SERIES, TO
DETERMINE THE DESIGNATION OF ANY SERIES AND TO FIX THE NUMBER OF SHARES OF ANY
SERIES. THE CORPORATION WILL FURNISH WITHOUT CHARGE TO EACH STOCKHOLDER WHO SO
REQUESTS A STATEMENT OF THE POWERS, DESIGNATIONS, PREFERENCES AND RELATIVE,
PARTICIPATING, OPTIONAL OR OTHER SPECIAL RIGHTS OF EACH CLASS OF STOCK OR SERIES
THEREOF AND THE QUALIFICATIONS, LIMITATIONS OR RESTRICTIONS OF SUCH PREFERENCES
AND/OR RIGHTS.

     The following abbreviations, when used in the inscription on the face of
this certificate, shall be construed as though they were written out in full
according to applicable laws or regulations:

<TABLE>
<S>                                                      <C>
  TEN COM   -as tenants in common                        UNIP TRF MIN ACT__________ custodian (until age ______________)
  TEN ENT   -as tenants by the entireties                                   (Cust)
  JT TEN    -as joint tenants with right of                                        _____________ under Uniform Transfers
             survivorship and not as tenants                                       Minors
                            in common                                              to Minors Act________________________
  COM PROP  -as community property                                                                      (State)
</TABLE>


    Additional abbreviations may also be used though not in the above list.

  FOR VALUE RECEIVED,____________________________ hereby sell, assign and
transfer unto

  PLEASE INSERT SOCIAL SECURITY OR OTHER
  IDENTIFYING NUMBER OF ASSIGNEE
  ------------------------------

  ------------------------------

________________________________________________________________________________
(PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS, INCLUDING ZIP CODE, OF ASSIGNEE)

________________________________________________________________________________

________________________________________________________________________________

__________________________________________________________________________shares
of the common stock represented by the within Certificate, and do hereby
irrevocably constitute and appoint

________________________________________________________________________Attorney
to transfer the said stock on the books of the within named Corporation with
full power of substitution in the premises.

Dated ________________________________

             ___________________________________________________________________
             NOTICE: THE SIGNATURE TO THIS ASSIGNMENT MUST CORRESPOND WITH THE
                     NAME(S) AS WRITTEN UPON THE FACE OF THE CERTIFICATE IN
                     EVERY PARTICULAR, WITHOUT ALTERATION OR ENLARGEMENT OR ANY
                     CHANGE WHATEVER.

Signature(s) Guaranteed:


By_________________________________
THE SIGNATURE(S) SHOULD BE GUARANTEED BY AN ELIGIBLE GUARANTOR INSTITUTION
PURSUANT TO S.E.C. RULE 17Ad-15.